Mount St. Helens - Disturbance Zones Map

The May 18, 1980 eruption of Mount St. Helens involved a complex series of events that unfolded over 12 hours, with many events going on simultaneously. These volcanic events buried some areas in debris avalanches and mudflows, scoured other areas with hot gases, blew down or scorched forests on slopes several miles away, and dusted forests farther away with volcanic ash. Entire forests were toppled by the hot blast. Most plants and animals perished, meadows were destroyed, and numerous new ponds and lakes were created.

The eruption included many types of physical forces, such as heat, burial, and scour, and the intensity of these forces varied substantially over the blast area (for example, thin versus thick deposits, warm versus searing hot temperatures). Generally, these physical forces were most intense in areas closest to the volcano’s north side and less severe farther away, but the mountainous terrain shielded some spots from heat and funneled mudflows into stream valleys. Also, multiple forces affected many places. So, although the whole landscape looked gray and ashen, scientists found complicated patterns of disturbance and tremendous variation, or heterogeneity, in the effects on the ecosystems. Ultimately, the eruption created a complex mosaic of disturbance zones.

Browse the thumbnails below to learn more about the disturbance zones created by the eruption.